A multi-output DC-DC converter includes a step-down DC-DC converter circuit which includes a switching device for switching an input DC voltage to convert it to a pulse voltage, a choke coil and a smoothing capacitor for smoothing the pulse voltage to obtain a first output lower than the input DC voltage, and a flywheel rectifying device for causing a current to flow through the choke coil when the switching device is off; and a rectifying circuit for processing and rectifying the pulse voltage in the DC-DC converter circuit to obtain a second output. Since the flywheel rectifying device is a bi-directional synchronous rectifying device which is turned on when the switching device is off, even when the load current of the first output decreases, the amplitude of the source voltage of the switching device is not reduced. Therefore, the second output obtained from the rectifying circuit always maintains a normal value.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A multi-output DC-DC converter comprising a step-down DC-DC converter circuit comprising: a switching device for switching an input DC voltage to convert it to a pulse voltage; a choke coil and a smoothing capacitor for smoothing the pulse voltage to obtain a first output lower than the input DC voltage; and a flywheel rectifying device for causing a current to flow through the choke coil when the switching device is off; and a rectifying circuit for processing and rectifying the pulse voltage of the DC-DC converter circuit to obtain a second output, wherein the flywheel rectifying device is a bi-directional synchronous rectifying device which is turned on when the switching device is off.
2. The multi-output DC-DC converter according to claim 1 , wherein the choke coil is a transformer of which a secondary winding is connected to the rectifying circuit.
3. The multi-output DC-DC converter according to claim 1 , wherein the rectifying circuit comprises a coupling capacitor and a diode.
4. The multi-output DC-DC converter according to claim 2 , wherein the rectifying circuit comprises a coupling capacitor and a diode.
5. The multi-output DC-DC converter according to claim 1 , wherein the flywheel rectifying device comprises a switching transistor.
6. The multi-output DC-DC converter according to claim 5 , further comprising a diode in parallel to the flywheel rectifying device to ensure that current flows through the choke coil when the switching device and flywheel rectifying device are off.
7. The multi-output DC-DC converter according to claim 5 wherein the switching transistor comprises a MOS FET.
8. An electronic apparatus having a multi-output DC-DC converter, the DC-DC converter comprising a step-down DC-DC converter circuit comprising: a switching device for switching an input DC voltage to convert it to a pulse voltage; a choke coil and a smoothing capacitor for smoothing the pulse voltage to obtain a first output lower than the input DC voltage; and a flywheel rectifying device for causing a current to flow through the choke coil when the switching device is off; and a rectifying circuit for processing and rectifying the pulse voltage of the DC-DC converter circuit to obtain a second output, wherein the flywheel rectifying device is a bi-directional synchronous rectifying device which is turned on when the switching device is off.
9. The electronic apparatus according to claim 8 , wherein the choke coil is a transformer of which a secondary winding is connected to the rectifying circuit.
10. The electronic apparatus according to claim 8 , wherein the rectifying circuit comprises a coupling capacitor and a diode.
11. The electronic apparatus according to claim 9 , wherein the rectifying circuit comprises a coupling capacitor and a diode.
12. The electronic apparatus according to claim 8 , wherein the flywheel rectifying device comprises a switching transistor.
13. The electronic apparatus according to claim 12 , further comprising a diode in parallel to the flywheel rectifying device to ensure that current flows through the choke coil when the switching device and flywheel rectifying device are off.
14. The electronic apparatus according to claim 12 , wherein the switching transistor comprises a MOS FET.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
October 15, 2001
November 26, 2002
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